Composition of a premilled butadiene-acrylonitrile copolymer and a nonrubbery thermoplastic synthetic resin



Patented Sept. 15, 1953 UNITED STATES PATENT OFFICE A PREMILLED BUTA- ITRILE COPOLYMER COMPOSITION OF DIENE ACRYLON AND A NONRUBB SYNTHETIC RESIN Andrew F. Sayko and John R. Briggs,

ERY THERMOPLASTIC assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application April 12, 1949, Serial No. 87,138

11 Claims. (Cl. 260-455) an self-retractible to substantially original size and shape) synthetic rubber and certain thermoplastic synthetic resins which are hard and inelastic, that is, non-elastic (non-rubbery) polymers at ordinary temperatures. The final products range in flexibility from those resembling soft leather to very tough, hard, yet resilient, molding compositions, according to the resin to synthetic rubber ratio.

U. S. Patent No. 2,439,202 describes the preparation of thermoplastic compositions by mixing butadiene-acrylonitrile copolymer with a styreneacrylonitrile copolymer. However, the resulting composition is baggy and possesses a rough. grainy surface and is not easily workable.

The present invention is particularly concerned with a thermoplastic composition composed essentially of a blend, that is, a homogeneous mixture of a normally rubbery copolymer of butadiene-l,3 and acrylonitrile, with a hard, thermoplastic resinous polymer or copolymer which is non-rubbery at room temperatures, and which may even be brittle at room temperatures, e. g., polystyrene, polyvinyl chloride, a copolymer of styrene and isobutylene, as described in U. S. Patent No. 2,274,749, a copolymer of styrene and butadiene and a copolymer of styrene and acrylonitrile :as described in U. S. Patent No. 2,140,048.

The elastic synthetic rubber component is a 1,3-butadiene-acrylonitrile copolymer type rubher and is disclosedin U. S..Patent No. 1,937,000 and is a, well-known article of commerce. According to the present invention the synthetic rubber component is given a pretreatment prior to its incorporation into the synthetic resin component.

In accordance with the present invention, a series of butadiene-acrylonitrile copolymers were subjected to Mooney viscosity and gel content tests with the following results:

2 min. Mooney at 212 F.

Polymer g f 1 Low Mooney due to breakdown in absence of a heat stabilizer.

A-butadiene (657)acrylonitrile(35%) copolymer.

B-butadiene(82%gacrylonitriiegl8%) copolymer.

Obutadiene(74%)acrylonitri1e 26%) copolymer.

D-butadiene(65%)-acry1onitrile(35%) copolymer (low Mooney).

ano breakdown.

I2polymer broken down on cold mill.

cpo1ymer plasticized with xylyl mercaptan In a Banbury mixer for minutes at a temperature of 330 F.

d-mi1ied for minutes at a temperature 013-330 F.

c-millecl for 30 minutes at a temperatureoi 330 F.

f-milled for 10 minutes at a temperature at 330 F.

% by weight of the hard resin result in tough,

fiexiblejleather-like materials While those containing above 50% and up to of theresin rubber mix, result in molding compositions which can be shaped or formed to any desired contour jgel polymers also served With even pressure. All of the compositions are smooth and pliable and very easily worked.

iChe following example illustrates the beneficial efiect of the pro-milling on the final composition.

Each of the butadiene-acrylonitrile (65-35%) copolymers (polymer A) was blended with five difierent resins in the proportion of resin and 30% butadiene-acrylonitrile polymer. In each case the resin was first banded on the hot vided by means of a warm-up mill.

The listed data show the comparative extrusion rates and physical appearance of the extruded rods:

Extrusion properties of b the polystyrene, making the milling operation much easier.

Increases in extrusion rate of the order of 42% and 34% were obtained by employing high gel polymers in the isobutylene-styrene polymer resins. Although these resins perform satisfactorily on the mill, a smoother working blend results from the use of the treated polymers.

With polyvinyl chloride the trend toward mill with subsequent addition of the butadiene- 0 higher extrus on rates and lower tube swell is acrylonitrile polymers. The performance of again pp Gains of 76% and 105% re each m d i summarized b l realized by the substitution of the modified polymers.

Polymer The styrene-:butadiene copolymer resin h used Mlllmg charactenstws ofblend cellent processmg propert1es of its own. The ad- I v dition of treated butadiene-acrylonitrile rubber,

Aa Stock became baggy after Perbunan addition. A however, augments these properties COnSiderablY- ragga; grainy surfac was obs rv after thorough Extremely high extrusion rates and very low Ab Slight agging during Perbunan 5971191 1 M di swell values are obtained. Increased smoothness Continued milling produced a very rough surface. polymers.

M t ttti,iitiittitsttt35132? A h 331393031139 13 t above easements was Af Blending was rapid with no bagging. The resulting obtained In the fOlIOWlIlg manner:

mix was smooth and wor 4 About 0.2 g. of polymer (accurately weighed to at least .001 g.) is cut into cubes of about 1 In order to further demonstrate processing on the edge d pl ced in a 125 m1. Erlen variations in the various blends an extrusion m y r flask. O e hundred ml. of benzene is then tudy was performed ith th B 1 exadded to the flask, after which it is stored in truder. A constant speed of 80 R. P. M. was held the dark and all room t p ature for 48 hours.

throughout the test. Pre-heatd strips were pro- 36 At no time are the flask and its contents a t to hasten dissolution of the polymer.

A filter is prepared from 250 mesh stainless steel or Monel metal screen. A section of the screen 3.5" in diameter is cut out and folded utadiene-acrylonitrile copoZymer-resin blends mately. a 22%. and a 15 dition of the heat-treats .nitrile--26% resin and dime-65 acrylonitrile to decrease the tack of 75 Resin Styrcne-acryloni- 7 P1 t g f fg. Polyvinyl chlo- Styrene-butadiene trile copolymer 0 ys-yrene u y en ride-Extrusion copolyrnerEx- Pl Extrusion propfig ggg 'gl g' -:g; gg properties at 280 trusion properties 0 ymer erties at 315 r. s at R P F. at 280 F Appe r 5-3; is is sois as is is 3g. 3g s3 ,5 o o E. c1 c: 5 rs 0'" ,5 :5 w ,5 5

A H41 Rough and pliable.

Do. 74 Smooth and 11111 1 71 Do.

17.2 94.0 4. 88 23.0. 98.1 4.27 38.5 92.4 2.40 Smooth 20.5 85.3 4.16 29.3 114.6 3. 91 41.3 73.6 1. 73 104.0

23.0 34.3 3.69 34.0 112.8 3.31 56.0 93.4 1.67 1120 Very Smooth 14.0 66.8 4.77 29.7 104.8 3.52 31.3 64.5 2.06 31. 12.9 61.9 4.80 27.3 106.0 3. 31 38.0 73.1 1.92 95. 16.0 74.9 4. 68 32.8 116.3 3.54 64.3 114.6 1.78 105. 16.1 72.3 4.49 40.0 122.5 3.06 52.0 78.4 1.51 120.

From the above data it is evident that both the as filter paper. This folded screen is then placed butadiene-T l%acrylonitrile-25% resin and butain a 50 ml. beaker and brought to constant weight --.diene-%-acrylonitrile35% resin demonstrate by heating for a few hours in an air or vacuum an-improvement in the processability of resin 65 oven. blends when the nitrile polymers have been heat- The screen, after W i g, is placed in a funtreated to produce high Mooney and gel values. nel and the contents of the flask swirled a few .The processing advantage is shown by the higher times and then poured through it. The flask extrusion rates and the lower swell of the tubes. 1s r1nsed with about 20 m1. of solvent and this is Data for blends with pol styrene show apprOXlalso poured over the residue on the screen. wh

solvent has stopped dripping from the screen, it is returned to the tared beaker and weighed. In making this weighing, 1 minutes are allowedto elapse from the time solvent has ceased draining to the time the weighing is made. Since solvent is lost rapidly during this time, the balance can be adjusted so as to enable one to obtain weights at the given time in each measurement. This weight should be reproducible to 0.01 g.

After weighing the beaker, screen and wet gel, they are placed in an oven and brought to constant weight. Thus the percent gel in the polymer is calculated as follows:

(wt. beaker-l-screen-l-dry gel) (wt. beaker-l-screen) X100 1n1t1al polymer weight Wt. dry gel initial polymer wt. The swelling index is defined as follows: Swelling index= (wt. beaker-l-screen-I-wet gel) wt. wet gel (wt. beaker-l-screen-l-dry gel) wt. dry gel The nature and objects of the present invention having thus been set forth and specific examples of. the same given, what is claimed as new and useful and desired to be secured by Letters Patent is:

1. A composite thermoplastic homogeneous composition consisting of a mixture of a normally rubbery copolymer of butadiene-1,3, and acrylonitrile which has been separately premilled at 330 F., for to 30 minutes and a hard normally thermoplastic resin chosen from the class consisting of polystyrene, polyvinyl chloride, a copolymer of styrene and isobutylene, and a copolymer of styrene and aorylonitrile, said thermoplastic resin comprising from to 90% by weight and said rubber copolymer correspondingly comprising from 75 to 10% of the rubberresin mixture.

2. Product according to claim 1 in which the resin is present to the extent of 70% by weight and said rubbery copolymer to the extent of and in which the rubbery copolymer is milled for 15 minutes at 330 F., prior to being mixed with said resinous copolymer. i

3. Product according to claim 2, in which the resin is a copolymer of styrene and acrylonitrile.

4. Product according to claim 2, in which the Percent gel= 6 resin is a copolymer of styrene and isobutylene.

5. Product according to claim 2, in which the resin is polystyrene.

6. Product according to claim 2, in which the resin is polyvinyl chloride.

'7. The process which comprises milling a normally elastic rubbery butadiene-acrylonitrile copolymer at a temperature of 330 F., for 10 to 30 minutes and combining the mixture of rubbery copolymer solely with a normally inelastic thermoplastic resin selected from the group consisting of polystyrene, polyvinyl chloride, styreneacrylonitrile copolymer, isobutylene-styrene copolymer, and styrene-butadiene copolymer, said thermoplastic resin comprising from 25 to 90% by weight and said rubbery copolymer correspondingly comprising from to 10% of the rubber-resin mixture.

8. Process according to claim 7 in which the resin is a copolymer of styrene and acrylonitrile.

9. Process according to claim 7 in which the resin is a. copolymer of styrene and isobutylene.

10. Process according to claim 7 in which the resin is polystyrene.

11. Process according to claim 7 in which the resin is polyvinyl chloride.

ANDREW F. SAYKO. JOHN R. BRIGGS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,439,202 Daly Apr. 6, 1948 2,459,739 Groten et a1. Jan. 18, 1949 2,505,349 Daly Apr. 25, 1950 2,600,024 Romeyn et al. June 10, 1952 OTHER REFERENCES White et al.: Ind. & Eng. Chem, Pp. 770-775, August 1945.

Schoene et al.: Ind. & Eng. Chem, pp. 1246- 1249, December 1946.

Young et al.: Ind. 8: Eng. Chem, pp. 1446- 1448, November 1947.

Schmidt and Marlies: Principles of High Polymer Theory and Practice, p. 268, pub. 1948, by McGraw-Hill Book Co., N. Y. 

1. A COMPOSITE THERMOPLASTIC HOMOGENEOUS COMPOSITION CONSISTING OF A MIXTURE OF A NORMALLY RUBBERY COPOLYMER OF BUTADIENE-1,3, AND ACRYLONITRILE WHICH HAS BEEN SEPARATELY PREMILLED AT 330* F., FOR 10 TO 30 MINUTES AND A HARD NORMALLY THERMOPLASTIC RESIN CHOSEN FROM THE CLASS CONSISTING OF POLYSTYRENE, POLYVINYL CHLORIDE, A COPOLYMER OF STYRENE AND ISOBUTYLENE, AND A COPOLYMER OF STYRENE AND ACRYLONITRILE, SAID THERMOPLASTIC RESIN COMPRISING FROM 25 TO 90% BY WEIGHT AND SAID RUBBER COPOLYMER CORRESPONDINGLY COMPRISING FROM 75 TO 10% OF THE RUBBERRESIN MIXTURE. 